1. Field of the Invention
The invention relates to a de-interlacing method and related system, and more particularly, to a pixel interpolation method and related system thereof.
2. Description of the Prior Art
In traditional TV field, video data are broadcasted utilizing an interlacing method. When the interlaced video data is displayed on a digital TV, a de-interlacing procedure should be performed in order to transform the interlaced-scanned video data into progressive-scanned video data. The progressive scan doubles the scan frequency of the interlaced scan.
There are two techniques utilized for de-interlacing. The first technique is to merge an odd field and an adjacent even field into a frame. The second technique is to interpolate the frame.
However, an image is not always still due to motions in a frame. So the even field and the odd field do not correspond to the same picture. As a result, when the two fields are merged, the saw tooth problem occurs. On the other way, interpolation can improve the saw tooth problem. Therefore, when an image is not still, the interpolation method is often utilized instead of the field merging method.
Unfortunately, the interpolation method also has its problems. For example, a scan line can be generated by interpolation utilizing an upper scan line and a lower scan line. FIG. 1 illustrates an interpolation of pixels according to the prior art. Three scan lines respectively comprise 9 pixels P11P12P13P14P15P16P17P18P19, P21P22P23P24P25P26P27P28P29, and P31P32P33P34P35P36P37P38P39. Furthermore, we assume that the picture to be displayed is a black inclined plane. Therefore, the 9 pixels of the first scan line have corresponding pixel values 0, 0, 0, 0, 0, 0, 255, 255, and 255, and the 9 pixels of the third scan line have corresponding pixel values 0, 0, 0, 0, 255, 255, 255, 255, and 255. Please note that the pixel value 0 represents that the grey level is black, and that the pixel value 255 represents that the grey level is white. Theoretically, if the first and the third scan lines are utilized to interpolate the second scan line, the 9 pixels of the second scan line should have corresponding pixel values 0, 0, 0, 0, 0, 255, 255, 255, and 255 such that an ideal black inclined plane can be shown. However, the prior art averages the pixel values of the upper line and the lower line. The result of this averaging causes the 9 pixels of the second scan line to actually have 0, 0, 0, 0, 128, 128, 255, 255, and 255. Therefore the entire picture generates significant pellets due to the averaging pixel value 128.
Therefore, before the interpolation, an edge detection can be performed. The edge detection will detect whether an edge of each picture exists. FIG. 2 is a diagram illustrating the edge detection according to the prior art. Each scan line also has 9 pixels P11P12P13P14P15P16P17P18P19, P21P22P23P24P25P26P27 P28P29, and P31P32P33P34P35P36P37P38P39. As mentioned above, the first scan line and the third scan line are utilized to interpolate the needed second scan line. However, before the interpolation, each pixel P2× of the second scan line is utilized as a center to search possible edge angles. For example, in a case of pixel P25, the pixels P16 and P34 are utilized to detect whether 45 degrees is a possible edge angle. In the case of FIG. 1, the interface between the black inclined plane and the white background has a tan−12/2 edge angle. Therefore, after the correct tan−12/2 edge angle is detected, the pixels P16 and P17 on the first scan line and the pixels P34 and P35 on the third scan line are utilized to correctly interpolate pixel values 0 and 255 of the pixels P25-P26 on the second scan line. This can solve the above-mentioned problem.
Unfortunately, the interpolation procedure fails when the edge detection is performed because a wrong detection may occur so that an incorrect edge angle is detected. In other words, the interpolation method is incorrect and the displayed picture image will have a serious distortion for the person viewing.